Immediate Occurrence of Trichromatic Vision When Necessary Photopigments are Expressed
Topic This article lists and discusses items about immediate occurrence of trichromatic vision when necessary photopigments are expressed. Particularly Relevant Items Mancuso, K., Mauck, M.C., Kuchenbecker, J.A., Neitz, M., and Neitz, J., "Chapter 72: A Multi-State Color Model Revisited: Implications for a Gene Therapy Cure for Red-Green Colorblindness", in Anderson, R.E., LaVail, M.M., and Hollyfield, J.G., Eds., ''Retinal Degenerative Diseases'', Advances in Experimental Medicine and Biology, Vol. 664, 2010, pp. 631-638: *Pages 631-632 describe a multi-stage color model proposed by DeValois and DeValois in 1993, extended to predict that human colorblindness can be cured by gene therapy to add a missing photopigment, without changing post-synaptic circuitry. *Page 633 describes how a gene cuplication event adding a new cone would adapt pre-existing visual circuit for new purpose, automatically giving a new red-green color dimension. *Page 636 proposes color vision circuitry such that addition of a third class of cone would immediately produce a red-green color dimension. *Page 637 argues for the possibility of curing human red-green colorblindness because required circuitry is already present--simply adding the missing photopigment to the retina should transform an adult dichromat to a trichromat, recapitulating what occurred during evolution in our primate ancestors. Mancuso, K., Hauswirth, W.W., Li, Q., Connor, T.B., Kuchenbecker, J.A., Mauck, M.C., Neitz, J., and Neitz, M., "Gene therapy for red-green colour blindness in adult primates", ''Nature'', Vol. 461, 8 October 2009, pp. 784-787: *Abstract on page 784, describes that adding third opsin in adult red-green colour-deficient primates produced trichromatic colour vision behaviour, without an early developmental process; there is potential that gene therapy could cure adult vision disorders. *Pages 784-786 describe gene therapy performed on adult squirrel monkeys missing an L-opsin gene; before treatment, the monkeys failed to distinguish colours near certain spectral neutral points from grey, but after about 20 weeks from treatment, they were able to discriminate blue-green from red-violet, indicating that they had trichromatic vision. *Page 786 suggests that the new colour vision dimension used pre-existing circuitry, and that there is a form of inherent plasticity in mammalian visual system. *Page 786 also acknowledges that it is not known whether the animal subjects have new internal red and green sensations. Bennett, J., "Gene Therapy for Color Blindness", ''The New England Journal of Medicine'', Vol. 361, No. 25, December 17, 2009, pp. 2483-2484: *Page 2483 describes Mancuso et al. (2009), above, and questions whether there was a learning effect during the 5 month time before results. *Page 2483 also discusses the risk-benefit ratio as not seeming favorable, in part due to risk of inflammation. *Page 2484 points out that treatment of other diseases might be more important, and concludes that Mancuso et al. (2009) have shown possibility of reprogramming neuronal wiring, which might be useful with complete achromatopsia, cone-rod dystrophy, or some maculopathies. Possibly Relevant Items Jacobs, G.H., Williams, G.A., Cahill, H., and Nathans, J., "Emergence of Novel Color Vision in Mice Engineered to Express a Human Cone Photopigment", ''Science'', Vol. 315, 23 March 2007, pp. 1723-1725: *The abstract on page 1723 describes inherent plasticity in mammalian visual system as permitting emergence of dimension of sensory experience due to gene-driven changes. *Page 1723 describes color vision as requiring both photopigments and neural wiring, summarizes arguments about effects of adding a new class of cone photoreceptors to primate retina, and asks questions about mammalian brain plasticity and evolution. *Page 1725 proposes that alterations in receptor genes might permit new discriminations in a plastic nervous system. Makous, W., "Comment on 'Emergence of Novel Color Vision in Mice Engineered to Express a Human Cone Photopigment'", ''Science'', Vol. 318, 12 October 2007, p. 196: *Page 196 argues that conclusions of Jacobs et al. (2007), above, about plasticity and new dimension of sensory experience are not justified by evidence. Jacobs, G.H., and Nathans, J., "Response to Comment on 'Emergence of Novel Color Vision in Mice Engineered to Express a Human Cone Photopigment'", ''Science'', Vol. 318, 12 October 2007, p. 196: *Page 196 indicates that the percepts of mice are speculative, but repeats authors' belief that extraction of chromatic feature is evidence of emergence of new dimension and indication of plasticity. Discussion